Optical frequency combs provide the next step toward the realization of quantum computers

Controlling the quantum-mechanical properties of microscopic particles is essential to the establishment of quantum computing, an extremely fast and powerful technology that would use the quantum state of atoms and molecules to store information rather than the electrical switches currently used in computers. Because a quantum bit is susceptible to environmental factors such as heat, researchers are developing control methods at temperatures approaching absolute zero. Dr. Svetlana Malinovskaya, Associate Professor of Physics at Stevens Institute of Technology, has been funded by the National Science Foundation (NSF) to investigate light-matter interactions in ultracold atomic and molecular systems in order to provide new methods of quantum control.

A hindrance to the advancement of quantum computing is a phenomenon known as decoherence, which can be described as a loss of the information stored in a quantum state to the environment. One proposed way to limit decoherence is to take advantage of the special properties of ultracold atomic and molecular systems. Satyendra Nath Bose and Albert Einstein predicted that matter would behave in a different manner at temperatures that approach absolute zero (0 K or −273.15 °C). Under such conditions, atoms and molecules must be described with quantum properties rather than classical properties, and quantum effects are observed even on a macroscopic scale. The state of matter in this condition is known as a Bose-Einstein condensate, and it is often considered to be the fifth state of matter. This state has considerable potential for quantum computing applications because of the lack of thermal motion interfering with coherence of the quantum system.

Dr. Malinovskaya is studying coherence properties of atomic and molecular systems at this state and lessening the impact of decoherence to preserve the specifically created coherent state that would store information in a prospective quantum computer. She is also investigating the dynamics induced by ultrafast optical frequency combs at these ultracold temperatures. Optical frequency combs are pulsed electromagnetic waves that measure transitional frequencies in atoms and molecules more accurately than any other tool. Researchers create optical frequency combs by using lasers to emit a sequence of brief, tightly spaced pulses of light, each lasting femtoseconds (a quadrillionth, or millionth of a billionth, of a second). They can then calculate the frequency of electromagnetic radiation with great precision by superimposing the unknown frequency with the known comb frequencies and measuring the difference between them.

Frequency combs aid in identifying and manipulating atoms and molecules, and they may be able to affect the way quantum systems decohere. Dr. Malinovskaya will investigate the interaction of frequency combs with deeply bound vibrational levels in ultracold molecules and develop quantum control methods to manipulate population transfer. For example, a molecular vibration can be excited by the frequency comb, causing the molecule to climb the ladder of vibrational states of the ground electronic state.

“Optical frequency combs have revolutionized research and applications in numerous areas, and I am pleased that Stevens will lead the effort to bring this new dimension to research on ultracold quantum control,” says Dr. Rainer Martini, Director of the Physics & Engineering Physics Department. “This grant award speaks volumes about Dr. Malinovskaya’s merits as a researcher and innovator in the field of theoretical physics.”

Dr. Malinovskaya will expose her students to this groundbreaking research by incorporating findings on applications of optical frequency combs into her graduate course titled “Methods of Quantum Control,” which focuses on advanced quantum control methods based on the latest developments in laser technologies.